An antenna in the communication products is an element mainly used for radiating or receiving signals, and generally, the features of antenna are determined by the parameters of operation frequency, radiation patterns, reflected loss, and antenna gain, etc. According to different operation requirements, the functions equipped in the communication products are not all the same, and thus there are many varieties of antenna designs used for radiating or receiving signals, such as a dipole antenna, a rhombic antenna, a turnstile antenna, a triangular microstrip antenna, and an inverted-F antenna, etc.
A conventional dipole antenna applied in a wireless transmission device generally is a straight-line-typed dipole antenna. Referring to FIG. 1, FIG. 1 is a schematic diagram showing a conventional dipole antenna. Such as shown in FIG. 1, the conventional dipole antenna is composed of two symmetrical electrodes 20 opposite to each other, wherein those two electrodes 20 are located on the same plane of a substrate 10, and are electrically connected to feeding points 30. The aforementioned dipole antenna is commonly designed to obtain the antenna features of low Q value, high gain and broad bandwidth, and the method applied therein is generally directed to making the cross-sections of the twin electrodes 20 as large as possible for the dipole antenna. The dipole antenna having larger cross-sections can be made resonate at a lower frequency, and the length thereof can be shortened. Currently, a central-feeding-typed dipole antenna is a better choice, of which the impedance can be changed by adjusting the location of the feeding points 30, thereby making the impedance of the dipole antenna perfectly matching the impedances of transmission lines.
However, for the aforementioned conventional dipole antenna, the antenna performance can be promoted merely by focusing on the design of the length or thickness of the antenna electrodes, and the aforementioned technology still has quite a bottleneck for performance improvement. Further, with more enhanced circuit integration, the antenna design is also expected to be combined with the back-end circuit design, so as to make full use of an electric circuit board. However, conventionally, when an antenna is directly installed on an electric circuit board, the area surrounding the antenna on the electric circuit board usually has to be designed different from the other areas thereon, such as implementing different metallic layers on the area surrounding the antenna. Therefore, the conventional technology has quite a few design limitations and high difficulty level of process.
Hence, there is an urgent need to develop a dipole antenna which can be briefly merged into an integral circuit design, and has excellent antenna features of high gain and broad bandwidth, etc.